Supression of endothelial adhesion molecule up-regulation with cyclopentenone prostaglandins is dissociated from IkappaB kinase inhibition and cell death induction

Zernecke A, Erl W, Fraemohs L, Lietz M and Weber C
Source: FASEB J
Publication Date: (2003)
Issue: 17(9): 1099-1101
During inflammation processes, like after TNF-alpha stimulation, various adhesive interactions between endothelial cells and the blood constituents are changed in order to recruit circulating leukocytes to the site of inflammation. The adhesive properties is mediated by cell surface proteins termed ?cell adhesion molecules? (CAM). The TNF-alpha-induced increased of CAM expression is regulated by NF-kappaB. In this regard cPG (cyclopentone prostaglandins) inhibit IkappaB-alpha kinase (IKK) which in turn inhibits apoptosis through NF-kappaB. To further elucidate this mechanisms the authors nucleofected HUVEC with an IKK mutant resistant to cPG. Cells were then treated with PGA1 (a cPG) and stimulated with TNF-alpha. CAM expression was analyzed by flow cytometry. The results indicate that IKK inhibition is not required for the suppression of endothelial CAM induction.
The cyclopentenone prostaglandins (cPG) 15-deoxy-Delta12,14-prostaglandin J2 (dPGJ2) and PGA1 can inhibit multiple steps in nuclear factor (NF)-kappaB signaling and can induce cell death. Here we characterized the effects of dPGJ2 and PGA1 on the inflammatory induction of endothelial cell adhesion molecules (CAM). Pretreatment of endothelial cells with dPGJ2 or PGA1 at low concentrations dose dependently inhibited the up-regulation of CAM expression and monocyte arrest by tumor necrosis factor (TNF)-alpha but not expression of inhibitor of apoptosis proteins. Only at high concentrations, cPG enhanced TNF-alpha-induced cell death and inhibited TNF-alpha-induced IkappaB-alpha kinase (IKK) activation, IkappaB-alpha degradation, and NF-kappaB/p65 translocation, while promoting AP-1/c-jun phosphorylation. Expression of an IKK-beta mutant (C179A) resistant to interaction with cPG impaired cell death induction but not inhibition of CAM up-regulation by cPG. Gel shift and reporter gene analysis revealed that cPG at low concentrations directly impaired DNA binding of NF-kappaB and NF-kappaB-dependent transactivation. The synthetic analogs dPGA1 or dPGA2 were ineffective, indicating structural specificity of cPG. Thus, the suppression of endothelial CAM up-regulation with cPG is dissociated from cell death sensitization and IKK inhibition above threshold concentrations and related to interference with NF-kappaB binding. Our findings define distinct mechanisms for anti-inflammatory and proapoptotic effects of cPG in endothelial cells.